Coking of coals



Oct. 29, 1935.

W. FlTZ El AL COKING OF GOALS Filed April 7, 1952 6 Sheets-Sheet l W. FlTZ ET AL Oct. 29, 1935.

COKING 0F GOALS Filed April 7. 1932 6 Sheets-Sheet 2 Oct. 2-9, 1935. w. FiTZ El Al. 2,018,664

COKING OF GOALS Filed April 7. 1932 6 Sheets-Sheet 5 Oct. 29, w |Tz ET AL COKING OF GOALS Filed April 7, 1932 6 Sheets-Sheet 4 Fl .14- I0 I I1 79 P3 r :E' H 9 If W. FITZ El AL Oct. 29, 1935.

COKING OF COALS Filed April 7, 1932 6 Sheets-Sheet 5 JnvenTor':

W. FlTZ E1 AL Oct. 29, 1935.

COKING 0F COALS Filed April 7, 1932 6 Sheets-Sheet 6 ratent'ed Oct. 29, 1935 UNITED STATES PATENT OFFICE Application April '1,

In Germany 1932. Serial No. 003,832

April 8, 1931 9 Claims. (Cl. ZW-ZB) v The invention relates the-coking of coals and more particularly to the coking of coals in chamber coke ovens.

When coal is coked in coke ovens the gases and vapours generated therefrom are partially decomposed by the high temperature in the gas collecting space, whereby their composition is altered in a disadvantageous manner. In particular the tar contained in the products of distillation is much altered, and the benzol hydrocarbons are partially decomposed, so that the amount of higher homologues of the benzol is decreased and the yield of benzol hydrocarbons is lowered generally in comparison with the yield possible under more favourable conditions.

Apart from this decomposition, at the normal high temperature in the gas collecting space components of the gases formed in the preliminary, intermediate and subsequent degasiflcation stages react with one another in such a manner that the heavy hydrocarbons are decomposed by the omgen compounds contained in the gases of the preliminary degasifl'cation. The products of the stages of degasiflcation mentioned take variousroutes through the charge, and do not unite until they reach the gas collecting space, where the above mentioned undesirable reaction takes place. i

It is well known that in the coking process a so-called tar seam is formed, which gradually travels from the heated walls parallel thereto towards the centre of the oven. This tar seam is practically gas-impermeable in the case of most coals when coked in the ordinary way. The gases which form below the softening temperature of the coal, i.e. during the preliminary degasiilcation pass upwards to the gas collector between both tar seams through the cold and uncoked coal, whilst the gases formed during the softening and hardening of the coal and subsequently to the latter stage flow upwards outside the tar seam through the already coked portion of the charge and pass to. the gas collecting space through the fissures which appear in the coke. The richer in oxygen a coal is, the larger is the quantity of gases formed in the preliminary degasiflcation and the larger the content of oxygen compounds in these gases. It is only the mixing of the two different types of distillation products in the gas collecting space which at the temperatures usually obtaining there renders possible the undesired reaction of'the oxygen compounds with the heavy hydrocarbons.

The principal object of our present invention is to prevent the decomposition of the gases in the gas collecting space and the undesired reaction or the gases of the preliminary degasiflcation with the gases developed at higher temperatures. This is achieved according to the invention by providing on the surface of the coal charged into the chamber a covering layer whose permeability to heat is as small as possible, but which is completely permeable for the gases, and which during the coking process separates the gas collecting space from the coal space with a protective l0- effect against too high heating, and conducts the various products of degasiflcation separately from each other to the gas collecting space through its hollow pores or cavities.

' As by this means the gas collecting space can 15 be kept at considerably lower temperature than was formerly possible and as the various products of degasiflcation can only mix together at this low temperature, the defects pointed out above are avoided. Moreover a cooling action of the gases is produced, as they have to heat the covering layer which is introduced after the coal in a cold condition. By adding this layer in a moist state, rinsing with water or other evaporable liquids (preferably discontinued during the process in accordance with the cooling eiiect required), or using other cooling means, a part of their sensible heat can easily be withdrawn from the gases for the same purpose.

Coked fuels, such as small coke, loose ceramic materiahflint stones, or similar heat resisting substances on be used as the gas permeable heat insulating and cooling layer. These substances are introduced into the chamber above the ordinary coal charge, and canbe rinsed or sprayed with a liquid. This liquid is evaporated by the ascending hot gases and extracts the heat therefrom. Preferably the amount of rinsing or spraying is regulated in accordance with the required cooling action during the process. At the beginning .no rinsing or relatively little is necessary, as the gas-permeable, heat insulating material forming the covering layer can be introduced cold and with acertain moisture content. Water ispreferably used as the rinsing means as it possesses ahigh evaporation heat and can be separated from the gas in a simple manner. Instead of water however, tar, oils or other substances can be used, butthe use of oils has the disadvantagethat its evaporation heat is relatively low and that they can be decomposed by the high temperature of the gases.

When coked fuels .or loose ceramic bodies are used as the covering layer, the size of the material used has to be determined according to the type of coal under treatment. The standard which measures this is the degree of shrinkage of the coke in the chamber, the covering material can be prevented from falling between the coke cakes and the chamber wall by using sumciently large pieces. It is also possible to chute coarser material directly on the coal, and then material of smaller size, such as small coke. It

' is thus possible to use the well known method in the coking of coal by the tamping process, in which the coal cake is somewhat narrower than the coking chamber. It is also possible to do away with the spaces between the cake and the chamber walls either by adding coal or by breaking up the coal cake in the chamber, so that subsequently the covering layer can be brought onto the coal with the described effect.

The covering layer may also be composed of refractory bodies whose breadth approximately corresponds to that of the chamber. These refractory stones are in this case arranged one behind the other longitudinally of the chamber and are traversed by flues or channels which serve to conduct the distillation gases to the gas collecting space situated above the stones. In order to prevent prematuremixing of the gases of the inner distillation and the gases passing through the coked charge, these stones are provided with a number of flues or channels running breadthwise of the chamber, so that the gases of the inner distillation ascend through a central flue whilst the gases rising through the coked charge preferably ascend through flues situated further out.

The provision of the covering layer on the coal also has the advantage that owing to its weight it exercises a certain pressure on the coal charge, which continues during the coking process in spite of the charge of volume of the coal. Thus the formation of "foamy coke is considerably restricted. When refractory covering stones are employed this adaptation of the covering layer of the surface of the coal during the coking process is not possible to the same extent.

While the process according to our invention is being carried out the gas collecting space is preferably kept at such a temperature that neither transformation nor decomposition of the gas constituents takes place. On the other hand, the temperature in this gasspace must be above the dewpoint of the distillation gas for tar, in order to avoid condensation.

The gas collecting space can be cooled by leading off heat through the oven roof by reducing the thickness of .the latter whereby at the same time a reduction in the costs of erection is effected for the same size of coking space. If the thickness of the oven remained the same the introduction of a heat insulating gas permeable layer would naturally increase considerably the outer height of the oven. In order to avoid this defect the thickness of the heat insulating 00V? ering layer can be subtracted to a certain extent from the strength of the oven roof so that the height of a coke oven working according to this process would remain the same as heretofore without decreasing the capacity of the coking chamber.

In order to describe the nature of our present invention more in detail reference will now be made to the accompanying drawings in which:-

- Figs. 1 and 2 are sections taken through the coking chamber of a coke oven and the pushing machine arranged for carrying out the process according to the invention.

aoiaces Fig. 3 is a partial plan viewthereof showing the guide plates for receiving and forwarding the coke cake pushed out of the coking chamber.

Fig. 4 is a fragmentary section through the guide box or frame for the coke cakes along the 5 line IIIIII of Fig. 1.

Fig. 5 is a vertical section of the coking chamber taken through the upper part of the door of this chamber facing the expelling machine.

Fig. 6 is a cross section through the top 01a 10 freshly charged coking chamber.

Fig. '7 is a similar section showing the condition of the contents of the chamber after the coking.

Fig. 8 is a section corresponding to Figs. 6 and 15 7 of a somewhat different construction of the chamber with a fresh charge.

Fig. 9 is a similar section through this construction after the coking operation.

Fig. 10 is a fragmentary section similar to Figs. 10 6-9 through the top of a coking chamber which illustrated two further constructions.

Fig. 11 is a longitudinal section taken across the top of a number of coking chambers, showing a special construction of the upper covering of as the chamber.

Fig. 12 is a cross section through the top of a coking chamber showing a further construction of the walls and covering of this chamber.

Fig. 13 is a similar section through the top of so a coking chamber showing a construction in which the coal covering layer is formed of removable stone blocks traversed by flues or channels.

Fig. 14 is a similar section extending over a number of chambers showing a similar embodia ment togetherwith the device provided for lifting out the covering blocks.

Fig. 15 illustrates in side elevation a special construction of the device for moving the levellcr.

Fig. 16 is an elevation on a smaller scale of the 40 whole coke oven installation, seen from the coke side of the coke oven.

The brickwork of the coke oven battery I is erected on a continuous base or foundation in which the usual regenerators 3a are provided, 45 and contains the coking chamber 3 running transverse to the longitudinal axis of the battery and between these latter and separated there from by refractory walls 4, the heating chambers B. The coking chambers are closed at both 50 ends in known manner by removable doors 6, I, which extend over the whole height of the chambers and are gas air tightly sealed by suitable means. The upper roofing of the coking chambers and of the heating chambers is preferably 55 formed of brickwork 8 constructed of suitable thickness, into which the tops of the coking chambers 3 extend rather further than the heating chambers 5. i

At a certain distance from one longitudinal face of the oven battery and on rails 9 running parallel thereto the frame 10 of the coke pushing machine is movably arranged, which carries the pushing ram l2 adapted to move on rollers ll parallel to the longitudinal axis of the chambers 3 and carrying at the and facing the oven the pushing head l3 which is shaped in accordance with the cross section of the coking chambers. This ram'can be moved forward along the coking chambers by suitable devices after the two doors 6 and I have been removed for the purpose of expelling the coke cake from the chamber.

Along the other side of the battery and somewhat below the bottom of the coking chambers extends a continuous stage or platform M which carries two rails IS on which the frame |6 of the coke guide is adapted to travel. The latter possesses on two rails parallel to the longitudinal axis of the coking chambers and adapted to move by means of rollers a short distance transverse to the direction in which the car itself travels, the guide box l8 for the coke cake, so that after the door I has been removed the latter can be brought adjacent to the door aperture of the coke chamber in the path of the expelled coke cake by moving the car frame l6 on the rails l8 and subsequently pushing across the box l8. The distance apart of the vertical walls of the coke cake box is such that the cake can be pushed between them without breaking its structure.

n the oven roof 8 and parallel to the longitudinal axis of the battery rails l9 are disposed on which the frame 20 of the charging car is mounted, so that the lower outlets of the say, four coal supply hoppers 2| can be broughtover the charging openings 22 provided for each cok ing chamber in the oven roof 8. The charging car can also run beneath the corresponding outlets of a coal bunker and thus be filled in known manner with a quantity of coal sufiicient for one filling of a coking chamber.

For the purpose of levelling the surface of the coal charge 23 brought by this means into the coking chamber a leveller 24 is provided, which is movably mounted in known manner on the upper part of the expelling machine parallel to the longitudinal axis of the coke chamber.

In the construction shown in Figure 2 the leveller is supported by four rollers 25 which are each secured to the end of a bell crank lever 26 which is mounted on the expelling car frame III to rotate about the pivots 21. The downwardly pointing arms of the levers 26 are attached to a continuous horizontal push rod 28 which can be moved backwards and forwards a certain distance by means of a screw 29 provided at one of its ends and a nut rotatable thereon between stationary bearings and provided with a worm wheel 30 and a corresponding worm 3|. Thus by corresponding displacement of the push rod the rollers 25 carrying the leveller can be lowered together with the latter from the position shown boldly in Fig. 2 to the position shown in dotted lines.

The longitudinal movement necessary for advancing the leveller into the coking chamber is effected by means of a cord 32 which is secured at 33 to the leveller near the rearward end thereof and whose two ends run over the roller 25 and guide rollers 34 provided at the forward and rearward ends of the expelling machine frame to a pulley drum 35 to which they are secured, so that according to the rotation of the latter which is produced by motor power the forward or rear end of the cord is wound up on the drum and the other end simultaneously unwound. The upper end piece 36 of the ram |3 which is situated in the lower path of the leveller which serves for levelling the coal is mounted on the ram in such a manner as to be capable of pivoting forward by means of a hinge pivot. On a level with this path of movement a leveller opening 31 is provided in the body of the coke chamber door 6, which is adapted to be tightly closed by a flap and through which the leveller can be introduced into the coking chamber. By this means the uneven surface of the coal charge caused by coal heaping up beneath the charging openings is levelled down in known manner.

Besides the coal charging hoppers 2|, a number for instance four, of hoppers 38 for supplying the covering material are provided on the frame of the charging car 20 in such a manner that their discharge openings can be brought simultaneously over the four openings 22 of the chamber which has been previouslyfilled with coal. After the coal has been levelled the. cov- 1o ering layer 40 is shot onto the coal charge 23 by opening these discharge openings. Then the leveller 24 is raised to the position shown in heavy lines in Figures 1 and 2 by corresponding movement of the push rod 28 and of the rollers 25 connected therewith by the bell crank levers 26, in which position its forward tip is trapped in relation to .an upper leveller opening 4| closeable by a flap which is provided abovethe coal levelling opening 36 in the door 6 of the coking chamber. The leveller can be inserted again through this opening into the interior of the coking chamber and used for levelling the surface of the covering layer 40. In order to prevent the part of the loose covering layer situwhich projects such a distance that the slope of the covering material determined by its forward edge does not reach the upper forward edge of the coke cake. A similar retaining plate 42 is also provided on the inside of the rear door 1.

The gas collecting space 43 separated from the coal space of the coking chamber by the covering layer is connected near the forward end of the coking chamber by ascension pipe 44 with the usual so-called main 45 which extends the whole way along the front side of the battery 40 and serves for leading oif the products of distillation.

In order to separate the material of the covering layer from the coke cake when the latter is pushed out, a horizontal partition 46 is pro- 45 vided at the correct height between the side walls of the coke guide Hi, the channel 41 which forms between the upper outer part of the sides of the guide box is curved beyond the vertical termination of these guide walls laterally over a re- 5 ceiver 48 which serves temporarily to receive the covering material.

This separation of the loose material is not necessary when small coke is used. In this case the loose material can be pushed out with the coke cake into the quenching car and be separated later in the coke sorting stage.

The material of the coke cake falls through the rearward opening of the guide box into the receptacle 49 of the quenching car 50 which is stationed there during the pushing operation and can be moved along rails 5| at the coke oven battery. In order to prevent the covering material falling between the walls of the coke guiding box and the coke cake itself, horizontal supporting bars 52 covering this empty space are provided inside the box Walls l8 on either side at the level' of the upper edge of the coke cake or the partition 46. Longitudinal bars 53 having a similar effect may also be provided on the inside lateral walls of the coking chamber itself at the level of the covering layer in order to cover during the coking process but more particularly while the cake is being expelled, the spaces formed between the walls and the coke cake owing to In this case (Figs. 8 and 9) it is of advantage to arrange a number of such horizontal longitudls nal bars one above the other, the upper ones .projecting somewhat further than the lower so that they also have a certain supporting effect on the material lying above them.

In order to permit the gas collecting space to be kept cool by rinsing the covering layer with water or other suitable liquid, it is preferred to provide spray pipes 54 beneath the roof of the coking chamber, whose sections lying between the filling and other openings are connected with a ,feed conduit 55 lying on the roof of the oven.

the walls of the coking chamber lying at the level of the covering layer and gas collecting space, through which channels cooling agents consisting of water, vapour, air or suitable gases may be passed, either directly or through pipes inserted therein. (Fig. 12).

In order to facilitate the transference of heat to the atmosphere through the oven roof, the thickness of the latter may be decreased. For the same purpose the parts of the oven roof lying between the coking chambers may be closed with iron plates 58 and the openings of the coke chambers lying between their edges by special roofing stones 59 connected tightly but'looseably wherewith, whose downwardly opening undercut cavities are filled up with fire-resisting material. By pouring a layer of sand of suitable thickness on the top of this roofing the transference of heat can be regulated as required. In order in this case to make the oven roof accessible, it is preferable to mount on it by supports 69 a flooring 6i consisting of perforated sheet metal, which carries the rails l9 of the charging car.

In this construction illustrated in Figs. 13 and 14 instead of loose material uniformly shaped blocks 62 of fire-resistant material are used for separating the coal from the gas collecting space, which are suitably joined together in the breadth of the coking chamber and traversed by vertical channels 63 through which the gases rising from the coal during the coking process in the various zones of the oven breadth are carried upwardly separate from one another. The covering stones are each secured to the lower walls by the suspending rods 64 which in the construction according to Fig. 13 are led out through two vertical apertures 65 provided in the oven roof and sand sealing funnels 66 formed at the top of these apertures. The two rods are connected above the oven by a cross head 61 which is carried in the middle by a raising lever 68 which is mounted on a lever shaft 69 extending longitudinally of each coking chamber. On one end of this shaft a worm wheel 10 is secured whose worm H can be turned by means of a hand wheel I2 provided in an accessible spot at a convenient height. By the rotation of the shaft all the levers secured thereon and all the cover stones 62 suspended.

therefrom by means of the rods 64 are raised simultaneously towards the oven roof, and thus moved out of the range of the leveller or ram l3 12-. shrinkage of the coal during the coking process.

when the coal is being levelled or the coke cake expelled.

The suspending rods 64 'of the cover stones 62 lying beneath the charging openings preferably pass through two holes provided in the lid I2 5 covering said openings, and are provided at their upper ends with broadened heads so that they can be lifted out 'of' the coking chamber when the lid is removed. For this purpose, as shown in Fig. 14, it is preferred to provide on each of the lids a bracket 14 with which a lifting hook 16 engages which is mounted on a slide 11 to rotate about a pivot 16 and is connected with a weight loaded arm 19 in the manner of a bell crank lever, whichis connected by a cord I9 with a pulley 80. This pulley is firmly attached to a second pulley 8| of larger diameter from which a winding cord in the manner of' a differential pulley winding is guided to a winding drum 83' which is mounted near the side of the frame 20 20 of the charging car and can be driven by a motor M. The vertical lifting movement of the slide 11 and of the lid 13 connected therewith by the hook 16 which is to be produced is guided to a vertical rail provided on the side of the charging 25 car. For each of'the charging holes a lifting device of this type is provided on the charging car, so that all the lids can be lifted off at the same time and the cover blocks suspended therefrom withdrawn from the interior of the coking 30 chamber.

The lids can either remain hanging in the raised position whilst the coke cake is being expelled, or be put down meanwhile. After the coke cake has been expelled and the oven has been recharged with coal and levelled by means of the leveller the covering blocks 62 are replaced in their effective position on the top of the coal charge either by lowering the levers 68 or by setting on the lid 13 with the covering blocks suspended therefrom.

The lifting device for the leveller which serves the purpose of reversing the latter into the two different altitudes necessary for levelling the coal and the loose covering layer can, instead of being constructed as described with reference to Fig. 2, consist of a special guiding frame 85 (Fig.

15) in which the leveller is disposed between upper and lower guiding rollers 86 or 81 in such a manner as to move in its longitudinal direction, and can be raised and lowered by means of vertical spindles 88 which by means of bevel wheels 89 mounted on their lower ends and a horizontal driving shaft 90 connecting them can be rotated by a motor 9| at uniform speed in the directionfifi for raising and lowering. At the forward end of the guiding frame it is for instance preferred to mount a pivotal projecting arm 92 which carries at its free end a hook 93 which for the purpose of opening the lids of the two leveller openings 60 31, 4|, can be hooked into the locking clasps 94 of the latter and then raised, for which purpose a cord 95 is attached to the projecting arms 92 which runs over a roller provided above said arm on the guiding frame to a hand rotated winder 98. 65

in Figure 18. Near the coal bunker a similar smaller bunker 00 for the loose covering material is provided from which the material can be fed in suitable quantities into the corresponding hoppers 38 through four openings IOI.

Along the outside of the track of the quenching car 50 the usual coke bench I02 is provided onto which the coke is transferred from the quenching car after it has been quenched. Here it is devaporized and thereby cooled. The process according to the invention is however, not bound up with the employment of a quenching car, the coke cakes may be expelled directly onto the coke bench in order to be quenched and pulverized.

After being devaporized and cooled the coke is preferably transferred from the coke bench onto a horizontal conveyor band I03, which carries it through the intermediary of an ascending conveyor band I 04 to the collecting bunker I05 of the coke sorting plant. The small coke sorted out in this plant can be fed by means of a conveyor band I06 running beneath the outlets of the sorting plant and a bucket arrangement I01, to

the bunker 99 in order to be used as loose covering material.

We wish it to be understood that our present invention is not restricted to the special embodiment described and illustrated in the drawings. Our invention may be variosuly embodied as desired within in the scope of the claims hereinafter made.

We claim:

1. A method of carbonizing coal in an externally heated intermittent carbonizing retort chamber comprising charging a mass of coal into the retort chamber so as to leave a gas ofi-flow space above the top of the charge in said chamber, carbonizing the coal charge in said chamber by heat externally applied laterally inwardly of the carbonizing mass up to a level below the top surface of the coal charge, maintaining the coal charge stationary therein substantially throughout the carbonizing thereof, and after the chamber has been so charged but before all the charge has attained a temperature sufficient for heat decomposition thereof covering the top surface of the coal charge with a covering layer of a solid that is heat resistant and infusible at the maximum temperature of the charge while it is being carbonized and that is brought onto the top surface of the coal charge above the region of lateral application of the external heating and leaves a gas collecting space in the chamber above said covering layer, withdrawing distillate gases from the charge off into and through the gas collecting space left above the covering layer, and keeping the distillation gases that are in said space separated from the top surface of the carbonizing charge by said covering layer throughout the major part of the carbonization.

2. A method of carbonizing coal in an externally heated intermittent carbonizing retort chamber comprising charging a mass of coal into the retort chamber so as to leave a gas off-flow space above the top of the charge in said chamber, carbonizing the coal charge in said chamber by heat externally applied laterally inwardly of the carbonizing mass up to a level below the top surface of the coal charge, maintaining the coal charge stationary therein substantially throughout the carbonizing thereof, and after the chamber. has been so charged but before all the charge has attained a temperature sufficient for heat decomposition thereof covering the top surface of the coal charge with a cold covering layer of a solid that is heat resistant and infusible at the maximum temperature of the charge while it is being carbonized and that is brought onto the top-surface of the coal charge above the region of lateral application of the external heating and leaves a gas collecting space in the chamber above said covering layer, withdrawing distillate gases from the charge of! into and through the gas collecting space left abovethe covering layer, and keeping the distillation gases that are in said space sep- 10 arated from the top surface of the carbonizing charge by said covering layer throughout the major part of the carbonization.

3. A method of carbonizing coal in an externally heated intermittent carbonizing retort chamber 15 comprising charging a mass of coal into the retort chamber so as to leave a gas off-flow space above the top of the charge in said chamber, carbonizing the coal charge in said chamber by heat externally applied laterally inwardly of the carbonizing mass 20 up to a level below the top surface of the coal charge, maintaining the coal charge stationary therein substantially throughout the carbonizing thereof, and after the chamber has been so charged but before all the charge has attained a 20 temperature suflicient for heat decomposition thereof covering the top surface of the coal charge with a covering layer of a solid that is heat resistant and infusible at the maximum temperature of the charge while it is being carbonized and that 00 is brought onto the top surface of the coal charge above the region of lateral application of the external heating and leaves a gas collecting space in the chamber above said covering layer, withdrawing distillate gases from the charge off into to and through the gas collecting space left above the covering layer, and keeping the distillation gases that are in said space separated from the top surface of the carbonizing charge by said covering layer throughout the major part of the 4,0 carbonization and rinsing said covering layer with a liquid during the carbonizing.

4. A method as claimed in claim 1 and in which the covering layer is kept at a sufliciently high temperature as to avoid cooling the gases in the 45 gas collecting space below the dew-point for tar produced in the carbonization.

5. A method as claimed in claim 1 and which includes the further step of separating the covering layer from the carbonized charge upon 50 completion of the carbonization of the charge.

6. A method as claimed in claim 1 and which includes the steps of pushing the finished carbonized charge from the chamber and removing the covering layer from the chamber together 55 with the carbonized charge when the latter is pushed from the chamber, and separating the covering layer from the pushed carbonized charge outside the chamber.

'7. A method as claimed in claim 1 and in which 60 the covering layer is composed of small pieces of the material thereof and said pieces are of sufliciently low heat-conductivity as to retard flow of heat from the top of the carbonization charge into the gas off-flow space. 60

8. A method as claimed in claim 1 and in which thleI covering layer is composed of small pieces of co e.

9. A method of coking coal in a carbonizing retort chamber which comprises: charging the chamber with coal, leveling the charge to a top level below the top of said chamber, introducing onto the leveled top of the charge a covering layer of loose solid that is heat resistant and infusible at the maximum temperature of the charge while 15 it is being carbonized, leveling eald looee material. carbonizing the charae by heat externally applied laterally or the coal mass up to a level below the top surface of the coal shame. maintaining the covering layer on the coal charze above the region of lateral application oi heat externally throughout the major part otthe earhonimtion, and takingoflmevolvednomtheeoaltro ntbe chamber throuah the covering layer throughout the periodotthepreeenceoi theeoverlnzlayerand. after the carbonizing has been completed. removlnzthecarbonizedcharlelromthe chamberwlth the covering layer still resting thereon.

WILEILM mz. JOSEPH DANIIIB. 

